In what has now become a common technique a tubular string is expanded into a supporting relationship into a surrounding tubular by employing a swage driven in either an uphole of downhole direction. Other devices are also employed to perform the expansion. Frequently, steps are taken to enhance the nature of the grip between the expanded tubular and the surrounding tubular. In the past, this had been accomplished by the addition of threads to an end of the tubular to be expanded and the heat treating of that threaded zone while being careful not to treat the adjacent non-expanded zone. This technique had associated cost issues and had to be carefully executed to avoid creating situations that could result in failure of the expanded tubular. Alternatives that had been tried to an external thread on the tubular to be expanded by using a split ring but the small thicknesses that needed to be used due to low clearances during run in made it difficult to heat treat these rings without significant warping.
In the past, resilient seals were put in exterior grooves of sleeves mounted over a tubular to be expanded to minimize required expansion and to enhance the sealing contact after such expansion. One example of this technique is U.S. Pat. No. 6,098,717. This design was not directed at enhancing grip as much as improving the sealing contact after expansion. Other techniques that used traditional slip type structures on the exterior of the tubing to be expanded were limited in applicability to situations that involved substantial clearances during run in, making them impractical when close clearances were present.
What is needed and addressed by the present invention was a technique that could enhance grip in an expansion situation without increasing the force required to expand and be workable in a tight clearance environment. Another desirable feature for such a system is to eliminate the costs associated with the prior designs for heat treating. Accordingly, a variety of executions of the invention are described that feature a wire or wire-like material that can be solid or hollow and that is disposed and can be retained in a groove where the material is preferably harder than the two tubulars brought together during expansion and is so mounted that it need not be stretched or expanded with the inner tubular. These and other aspects of the invention will be more readily apparent to a person skilled in the art from a review of the description of the preferred embodiment and the claims that appear below.